# TagOverflow - an interactive graph of Physics.SE tags

I created a graph of tags from Stack Exchange sites (including Physics.SE), TagOverflow.

I made an interactive version of Map of 64 Tags from Physics.SE, with always up-to-date data.

Nodes represent the most popular tags, with their area being proportional to the number of questions with them.

Edges represent relation between tags. Their width is related to the number of questions with both tags, while their shade - how much more often they occur than one should expect by random chance.

Default coloring is due to community detection - automated splitting of a graph into densely connected subgraphs. Positions of the nodes are due to D3.js force layout. That is, nodes connected via an edge attract each other. The strength of such attraction depends on the strength of an edge. Plus, all nodes repeal each other at a short distance to prevent overlaps.

As Physics.SE is a (relatively) big place, it may be interesting to do conditional graphs (i.e. graphs restricted to question with a given tag), e.g. to get (TagOveflow: Physics: quantum-mechanics) or (TagOveflow: Physics: homework-and-exercises).

You can:

• check tag grouping - i.e. for the sake of eliminating synonyms or poorly-defined tags,
• try to infer the structure of physics from Physics.SE :).

Besides looking at the graph, you can:

• get interesting information per tag (e.g. top questions and users),
• get some statistics (like average score for these tags).

I hope you enjoy it!

Questions:

• are there any findings on Physics.SE tags you find insightful and would like to share?
• do you have ideas how to improve its usefulness or niceness to our community?
• Awesome, cool! Nothing more to add :) – Danu Feb 15 '15 at 16:29
• Nice! You should go make a similar graph for my question here: meta.stackexchange.com/questions/247794/… The data query is already in the answer! You just have to plot :) – tpg2114 Feb 15 '15 at 21:08
• @tpg2114 Thanks, but it is not "just" (i.e. not a one-liner). The easiest way to go would be data -> networkx in Python to convert it into graphml -> gephi.github.io. Or something like bl.ocks.org/mbostock/1153292 (but here, there is no obvious choice for node and edge size). – Piotr Migdal Feb 16 '15 at 11:07
• @PiotrMigdal The "just" was more tongue-in-cheek than serious. I actually have the code to get it into networkx so I could get it into graphml but I don't know how to use anything else after that step. – tpg2114 Feb 16 '15 at 22:44
• @tpg2114 Install Gephi, import this file into it (remember to check that it is a directed graph), position it and export. A similar instruction is here: github.com/stared/tag-graph-map-of-stackexchange/#usage. – Piotr Migdal Feb 16 '15 at 23:15
• You should make the canvas fit the entire page, so when we drag things, they dont go out of the edge of the box, and we have more room to move stuff around and observe groupings – J.Todd Feb 22 '15 at 17:50
• I find it extremely interesting that the tags associated with more advanced topics tend to have a higher average owner reputation. – Jim Feb 24 '15 at 22:09
• Fluid dynamics is surprising - it's more lonely than "soft question". – Selene Routley Feb 25 '15 at 11:13
• Very cool! Interestingly, looking at the average number of answers per question, [condensed-matter] seems to have the lowest average number of answers per question, even lower than e.g. [string-theory]. I wonder why that is (% answered is even more extreme). The average view count seems to be correlated to the number of answers per question, indicating we might have a shortage of condensed matter physicists. The average score and average owner reputation both seem to be higher in the ranking of tags so I don't think the questions are to blame. – Wouter Feb 27 '15 at 12:25

## Minor issue

It seems you have a link error. If you select a tag (I chose fluid-dynamics, but it works for others I've tested, including other SE sites), the link at the top, e.g., Physics:<tag> (<question_number>), leads to

which does not exist. It should be

https://physics.stackexchange.com/questions/tagged/fluid-dynamics

A quick look in main.js on your github page shows that /questions/ should be included (see line 315):

.attr('href', seSiteData.siteData.site_url + "/questions/tagged/" + tagName)


So I suspect the problem is elsewhere, but didn't investigate more since I'm not really well-versed (read: at all) in JavaScript.

## Feature request

Would it be possible to make a tag-graph of a particular user?

• Ooh! Single user graphs. That would be spiffy. Want. – dmckee --- ex-moderator kitten Feb 16 '15 at 18:48
• Thanks! Problem fixed (it was in another place). Graphs for a particular users - popular tags can be get (through /users/{ids}/tags), but not connections between them. So I think that the way to go is to probe last questions (well, for 100q per query, it is easy to get up to a few k of questions!). In short: possible: yes, but it will need writing some pars from scratch rather than just adding an option. – Piotr Migdal Feb 16 '15 at 21:32
• @PiotrMigdal: Aha, glad you found it! Though if I had enough patience, I probably could have found it ;) I had assumed the feature request would be non-trivial--it explains why it wasn't covered in the first place! It is a beautiful tool nonetheless. – Kyle Kanos Feb 17 '15 at 3:04